The present invention relates generally to methods and apparatuses for transporting light from a single light source to multiple locations, and more specifically, to a method and apparatus for transporting light from a single light source to multiple locations using a plurality of light fibers.
Optically transmissive materials, such as glass or polymers, may be used in a light guide to propagate light. A light guide typically includes at least one surface adapted to receive light from a light source and an optically smooth surface adapted to reflect light which is propagating along or through the light guide. Common examples of light guides include optical fibers of the type traditionally used in the data communication industry and, more recently, light fibers of the type disclosed in U.S. Pat. No. 4,422,719 (Orcutt) which are used for illumination purposes. Another example of light guides are the planar light guides used in the optical display industry. In these devices, at least one end of the surface of the light guide is adapted to receive light from a light source, and the light so received propagates between the two major surfaces of the light guide.
Multiple light fibers can be bundled together to form a light transport device that accepts light from a single source and emits light in different directions that are determined by the orientation of the output ends of the fibers. A known light transport device that employs a bundle of light fibers is disclosed in U.S. Pat. No. 5,058,985 (Davenport et al.). This device includes a series of fibers having input ends that are bundled together to form a light injection surface. Light is directed into the light injection surface from a light source. The amount of light injected or coupled into the fibers through the injection surface is increased by compressing the input ends of the fibers to reduce or eliminate voids between adjacent fibers. Light entering a void cannot be transmitted through the fiber and thus represents a diminution in coupling efficiency.
The technique described in Davenport et al. has a number of limitations, however. For example, the light fibers must be formed from a compression-deformable material. Hence, the technique precludes the use of non-deformable materials such as glass. In addition, a sleeve having a tapered bore is required for receiving and compressing the fibers. Also, the device requires cladding material, which surrounds the fiber core within the bundled input end. The cladding material consumes space within the bundle, so that proportionately less light can be introduced into the fibers (or, proportionately fewer fibers can be included within the bundle). Removing the cladding (which is not described in the ""985 patent) would constitute an extra costly and time-consuming step. Finally, compressing the fibers in the manner required by this patent may create non-uniformities through cross-sections of the fibers, which may introduce scattering points in the fibers.
There is thus a need in the art for a light transfer device comprising a plurality of fibers, each having first and second ends, wherein at least the first ends of the fibers are arranged into an injection surface that is substantially free of voids or cladding materials. There is also a need in the art for a method for making such a device which does not require compression deformation of the fibers in the vicinity of the injection surface or the use of a compression sleeve. These and other needs are met by the present invention, as hereinafter described.
In one aspect, the present invention relates to a light fiber which is prefabricated with a cross-sectional shape on at least a first end (hereinafter termed the xe2x80x9ccontacting endxe2x80x9d), the cross-sectional shape being such that a plurality of the fibers can be assembled with their contacting ends adjacent to each other so as to form a planar light injection surface which is substantially free of voids, cladding, and other non-light-guiding materials or features. The contacting ends have a prescribed cross-sectional shape prior to contacting one another such that, when they are brought into contact, the outer edges can assume an orientation completely contiguous with one another so that the light injection plane is substantially free of voids while each of the contacting ends maintains its respective prescribed cross-sectional shape.
In some embodiments of this aspect of the invention, at least one of the contacting ends has a noncircular cross-sectional shape. Such noncircular cross-sectional shapes include, for example, sectors or polygons (e.g., squares, rectangles, hexagons, etc.). In other embodiments, each of the plurality of contacting ends has a unique cross-sectional shape. In still other embodiments, at least one of the contacting ends has an irregular cross-sectional shape.
In another aspect, the present invention relates to a device which comprises a plurality of light fibers n1, . . . , nk wherein k is an integer greater than or equal to 2, wherein each of the fibers has a contacting end, and wherein the contacting ends are capable of being assembled into a coplanar orientation so as to form an essentially continuous input plane. Each of the k light fibers has a contacting end with a cross-sectional shape corresponding to a sector such that fiber ni has a sector with an arc length of ai that subtends an angle xcfx86i, wherein a1+ . . . +ak=2xcfx80 radians, and wherein xcfx861+ . . . +xcfx86k=360xc2x0. The radii of all k sectors are typically equal, i.e., the fibers can be arranged so that the sectors lie in the same plane and form a circle, although analogous embodiments are also possible wherein the sectors can be arranged to form an ellipse or other geometric shape. The arc lengths of all k sectors are also typically equal, i.e., a1= . . . =ak, although in some embodiments, at least two elements am, an of the set a1, . . . , ak are not equal, i.e., amxe2x89xa0an.
In another aspect, the present invention relates to a device comprising a plurality of fibers, each of the fibers having a contacting end, wherein the contacting ends are capable of being assembled into a coplanar orientation so as to form an essentially continuous input plane. Each of the contacting ends has a prescribed cross-sectional shape prior to contacting one another that is conformably coated by a cladding layer, the cladding layer comprising a material/substance having a refractive index less than that of the light fiber that comprises the contacting end. Preferably, the cladding layer is thin and constitutes a small percentage of the total surface of the continuous plane.
In the various embodiments of the various aspects of the present invention, the non-contacting end of at least one of the light fibers may have a circular cross-section. Alternatively, in some embodiments of the invention, the non-contacting end of at least one of the light fibers has a cross-sectional shape corresponding to the prescribed cross-sectional shape of its contacting end. In other embodiments, the non-contacting end of at least one of the light fibers has a cross-sectional shape different from the prescribed cross-sectional shape of the contacting end. In those embodiments where the contacting and non-contacting ends of a light fiber differ in shape, the light fiber may undergo a transition from the cross-sectional shape of its contacting end to the cross-sectional shape of its non-contacting end. This transition may occur over a predetermined portion of the length of the light fiber, which in some cases may be the entire length of the fiber.
In a further aspect, the present invention relates to a device comprising a plurality of light fibers, each having a contacting end. The contacting ends are arranged into a light injecting plane that is substantially free of both voids and non-light guiding material such as a cladding, i.e., the adjacent fiber cores are in direct contact with one another.
In yet another aspect, the present invention relates to a method for transporting light from a single source to multiple prescribed locations. In accordance with the method, light is directed into a light injection plane formed by a plurality of light fiber input ends. The input ends of each light fiber have a prescribed cross-sectional shape selected such that adjacent input ends have outer peripheries contiguous with one another so that the light injection plane is substantially free of voids or other non-light-guiding materials. The output ends of the light fibers are then oriented so that light emitted therefrom is applied to the respective prescribed locations.
In still another aspect, the present invention relates to a method for making a light transport device. In accordance with the method, a plurality of light fibers are provided, each having a contacting end and a non-contacting end. The contacting end of each of the light fibers has a prescribed cross-sectional shape prior to being brought into contact with one another. The prescribed cross-sectional shapes are selected so that, when the outer edges of the contacting ends are brought together in a given orientation, they contact one another in a completely contiguous manner. The contacting ends are then arranged in a light injection plane such that the outer edges of adjacent contacting ends are completely contiguous with one another so that the light injection plane is substantially free of voids and non-light-guiding material.